Stress-related mental illnesses, such as depression and anxiety disorders, are more prevalent in women than men. Dysfunctions in corticotropin-releasing factor (CRF), the neuropeptide that orchestrates the stress response, have been linked to depression and anxiety disorders. However, sex differences in the CRF system are not well characterized. Recent work from our laboratory identified sex differences in neuronal responses to CRF. Specifically, postsynaptic sensitivity of locus coeruleus (LC) neurons to CRF was greater in female vs. male rats. Moreover, swim stress sensitized LC neurons to CRF in male rats only. The following proposal will expand on these finding to determine the underlying cellular mechanism of these differences. The specific aims are as follows: 1) Identify sex differences in the coupling and signaling of the CRF receptor. CRF receptor immunoprecipitation will be used to determine whether there are sex differences in coupling of different G-proteins to the CRF receptor under stressed and unstressed conditions. Additionally, sex differences in CRF receptor signaling will be evaluated by using PKA and PKC assays. Preliminary data indicate that the CRF receptor is coupled more strongly to the Gs protein in unstressed females compared to unstressed males. Following swim stress, Gs coupling to the CRF receptor increases in males only. These are the first data to suggest sex differences in the coupling of a receptor to different G-proteins. Sex differences in CRF receptor structure and function may contribute to increased stress-susceptibility in women. 2) Identify sex differences in CRF receptor trafficking following stress. Here we will use immunoprecipitation of the CRF receptor, along with immunoelectron microscopy to determine whether the CRF receptor is trafficked differently in male vs. female rats after stress. Preliminary data suggest that following stress, CRF receptor internalization in females may be comprimised. If supported, this would suggest that female rats lack this compensatory stress response. PUBLIC HEALTH RELEVANCE Women are twice as likely to suffer from stress-related psychiatric disorders, like depression and anxiety disorders, as men. The proposed experiments will identify sex differences in the receptor for CRF, an important neuromodulator of stress, which may underlie the increased vulnerability of females to stress and stress-related pathology. Importantly, because CRF antagonists are being developed to treat depression and anxiety disorders, sex differences in the CRFr could impact the efficacy of these compounds in women.